In a known fashion, the friction existing between the movable valve body and the valve element of the valve that is integral with the housing, as soon as the valve is to be actuated, must be reduced to the relatively low value of sliding friction to ensure reliable response of the valve and especially to avoid the development of stick-slip effects, especially during the small strokes that correspond to only a fraction of the maximum control stroke. The time intervals within which certain functional positions and/or opening cross sections of flow paths in the valve are reached are kept as short as possible in this manner.
An exciting winding associated with one of the functional positions of the solenoid valve is energized, and a ripple is imposed on its exciting current that results in a pulsating rise and fall of the magnetic forces that "pull" the armature against the action of a return spring into its required position. This required position, which corresponds to a desired throughput cross section of the valve in this functional position, must result from the equilibrium of the magnetic positioning force generated by the excitation of the winding and by the restoring force of the respective acting valve spring, which increases with deflection of the armature. In order to achieve short switching times for solenoid valves controlled in this manner, powerful return springs must be used and high exciting currents must be generated to energize the exciting windings, powerful return springs to permit a rapid return of the armature to its basic position when the excitation is shut off, and high exciting currents in order to displace the armature sufficiently rapidly against the action of the powerful return springs. To accelerate the switching processes, as proposed in British 885,121, it is also possible, when shutting off the excitation of one exciting winding briefly, to excite the winding that produces magnetic forces in the opposite direction, but this would entail considerable control-engineering expense and/or considerable expense for additional control windings.